Drive apparatus for electric vehicle

ABSTRACT

A drive apparatus for an electric vehicle comprises a motor (1), a gear section (9) for transmitting rotation of a rotor shaft (2) of the motor to a wheel, and a case (10, 90) for accommodating the motor and the gear section. The case has a partition (12) that separates a motor chamber (m) for accommodating the motor and a gear chamber (g) for accommodating the gear section, and the partition has an orifice (53) that connects a lower portion of the motor chamber and the gear chamber. Supplying means (5) is provided for supplying oil from the gear chamber into the motor chamber in accordance with rotation of the gear section. Through the operation of the orifice, oil gathers in a lower portion of the motor chamber and, thus, the motor chamber serves as a reservoir. Thus, while employing a light-weight and compact-size construction that does not comprise an oil reservoir, the drive apparatus secures a sufficient amount of lubricating oil during stop of the vehicle, and reduces the stirring loss of the gear section and cools the motor with oil during the running of the vehicle.

TECHNICAL FIELD

The present invention relates to a drive apparatus for an electricvehicle and, more particularly, to lubricating means of a driveapparatus for an electric vehicle combining a motor and a gear sectionfor transmitting the drive force of the motor to wheels.

BACKGROUND ART

As one form of drive apparatuses for electric vehicles, there is a typeof apparatus that combines a motor and a gear section for transmittingthe drive force of the motor to wheels. In this type of drive apparatus,the gear section must be lubricated whether the motor is cooled by airor cooled by oil. Normally, since the gear section of the driveapparatus including a differential gear must be provided with asufficient amount of lubricating oil for the next start during stoppageof the vehicle, it is necessary that the oil level in the gear case behigh so that the entire differential gear case is immersed in the oil.In contrast, during the running of the vehicle, since the lubricatingoil is sufficiently distributed to each part of the gear section, thereis no need to keep the oil level high in the gear case as mentionedabove. On the contrary, the oil level needs to be reduced to a minimumrequired level, in order to reduce the stirring loss of the gearsection. In view of such circumstances, the specification of U.S. Pat.No. 5,295,413 discloses a technology that adjusts the oil level in thegear case as discussed above, by supplying oil to and discharging oilfrom an oil reservoir disposed in an upper portion of the gear case.

For drive apparatuses for electric vehicles, there is a strong demandfor weight reduction and size reduction, considering electric powerconsumption reduction for a travel distance increase and the problem ofinstallation of the apparatus in a vehicle. Viewing the aforementionedtechnology from this standpoint, the technology has problems of anweight increase of the drive apparatus caused by an increased size ofthe gear case since the oil reservoir is disposed in the gear caserequiring an oil reservoir space in addition to the space needed toaccommodate the gear section.

Accordingly, it is a first object of the present invention to provide adrive apparatus for an electric vehicle that has a light-weight andcompact-size construction and enables reduction of the stirring loss ofthe gear section during the running of the vehicle while securing asufficient amount of lubricating oil during stoppage of the vehiclewithout requiring an additional oil reservoir.

In addition, it is a second object of the present invention to enablethe circulation of lubricating oil for achieving the above objectwithout allowing the circulation to cause a drive loss.

Furthermore, it is a third object of the present invention to cool amotor while maintaining an appropriate oil level in the motor chamberduring the running of the vehicle and preventing a stirring loss due tothe rotation of the rotor.

DISCLOSURE OF THE INVENTION

To achieve the aforementioned first object, the present invention ischaracterized by comprising a motor including a stator and a rotorhaving a rotor shaft that is rotatable inside the stator, a gear sectionfor transmitting the rotation of the rotor shaft to a wheel, and a casefor accommodating said motor and the gear section, wherein the case hasa partition that separates a motor chamber for accommodating said motorand a gear chamber for accommodating said gear section, and thepartition has an orifice that connects a lower portion of said motorchamber and said gear chamber, and supplying means is provided forsupplying oil from said gear chamber into said motor chamber inaccordance with rotation of said gear section.

In the above-described construction, oil is supplied from the gearchamber into the motor chamber by the supplying means in accordance withthe rotation or revolution of the gear section or the motor during therunning of the vehicle. The oil supplied to the motor chamber is thenreturned to the gear chamber through the orifice of the partition. Inthis operation the oil level in the gear chamber decreases because theamount of oil supplied into the motor chamber by the supplying means isgreater than the amount of oil returned to the gear chamber through theorifice so that oil accumulates in the motor chamber In contrast, duringstoppage of the vehicle, the supplying means stops supplying oil fromthe gear chamber into the motor chamber since the motor and the gearsection stops revolving, whereas oil continues returning from the motorchamber to the gear chamber through the orifice of the partition. Thusthe amount of oil in the motor chamber decreases, and the oil level inthe gear chamber rises. Thereby, the apparatus reduces the stirring lossof the gear section during the running of the vehicle by lowering theoil level in the gear chamber, and provides a sufficient amount oflubricating oil for the gear section for a start by raising the oillevel in the gear chamber during stoppage of the vehicle. Thus, theapparatus utilizing the motor chamber as an oil reservoir, eliminatingthe need to provide an oil reservoir in the gear chamber and allowing acompact design of the gear case. In addition, since the oil can be heldin the motor chamber during the running of the vehicle, the stator canbe oil-cooled in a dipped state, thus enhancing the motor coolingeffect.

In addition, to achieve the aforementioned second object, the supplyingmeans comprises an oil receiver for gathering oil in the gear chamberdragged up by rotation of the gear section and leading it to the motorchamber.

Since this construction gathers an amount of oil in the gear chamberdragged up by rotation of the gear section, into the oil receiver, andsupplies it into the motor chamber, the drive apparatus for an electricvehicle can be reduced in size by simplifying the construction of thesupplying means.

Furthermore, to achieve the aforementioned third object, the apparatushas a construction where a window for communication between the motorchamber and the gear chamber is formed in a position that is above theorifice of the partition and at the same level as the lowermost positionof the peripheral face of the rotor.

Since the window for communication between the motor chamber and thegear chamber is provided in a position that is above the orifice of thepartition and at the same level as the lowermost position of theperipheral face of the rotor in this construction, the oil held in themotor chamber returns to the gear chamber through the window before oilreaches such a level that the rotor is dipped in oil. Thus, theprovision of the window enables setting an oil level in the motorchamber such that the rotor is not dipped, thus making it possible toavoid a stirring loss of the rotor while cooling the motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a drive apparatus for an electric vehicleaccording to a first embodiment of the present invention developed inthe direction of axis;

FIG. 2 is a view taken in A--A direction of FIG. 1;

FIG. 3 is an axial sectional view of a rotor and a stator illustratingan arrangement of oil passages in the motor of this drive apparatus;

FIG. 4 is a detailed perspective view of an oil receiver of supplyingmeans of the drive apparatus;

FIG. 5 is a sectional view of a drive apparatus for an electric vehicleaccording to another embodiment of the present invention developed inthe direction of axis;

FIG. 6 is a view taken in B--B direction of FIG. 5;

FIG. 7 is a sectional view taken in C--C direction of FIG. 6;

FIG. 8 is a view taken in D--D direction of FIG. 5;

FIG. 9 is a view taken in E--E direction of FIG. 5; and

FIG. 10 is a fragmentary axial sectional view where the supplying meansaccording to the second embodiment is modified in part.

BEST MODES FOR CARRYING OF THE INVENTION

Embodiments of the present invention will be described hereinafter withreference to the drawings. First, FIGS. 1-4 illustrates a firstembodiment. The construction of this apparatus will first be roughlydescribed. As shown in the axially developed sectional view of FIG. 1,the drive apparatus comprises a motor including a stator 4 and a rotor 3having a rotor shaft 2 that rotates in the stator 4, a gear section 9for transmitting rotation of the rotor shaft 2 to wheels (not shown),and a case that accommodates the motor 1 and the gear section 9 (formedby combining a motor case 10 and a gear case 90 as described belowaccording to this embodiment). The case has a partition 12 thatseparates a motor chamber m accommodating the motor 1 and a gear chamberg accommodating the gear section 9. The partition 12 has an orifice 53that connects a lower portion of the motor chamber m and the gearchamber g in communication. The partition 12 is also provided withsupplying means 5 for supplying oil from the gear chamber g into themotor chamber m in accordance with rotation of the gear section 9. Thesupplying means 5 has an oil receiver 51 for gathering oil in the gearchamber dragged up by rotation of the gear section 9 and guiding it tothe motor chamber m. A window 52 for communication between the motorchamber m and the gear chamber g is formed in a position that is abovethe orifice 53 of the partition 12 and at the same level as a lowermostposition of the peripheral face of the rotor 3 of the motor 1.

The aforementioned portions will be sequentially described below. Asshown in FIG. 1, the motor 1 comprises the motor shaft 2 supportedfreely rotatably at both ends on a motor case 10 by bearings 11, therotor 3 fitted to the rotor shaft 2 in a rotation preventing manner andprovided with a plurality of permanent magnets 31 corresponding innumber to the magnetic poles, and the stator 4 having a core 40 that isfitted on its outer peripheral face to the motor case 10 in a rotationpreventing manner by a key or the like and surrounds the outerperipheral face of the rotor 3, and coil ends 41 that protrude from theopposite axial ends of the core 40 where coil portions are inserted intoslots of the core 40. In FIG. 1, reference character 6 denotes aresolver attached to one end of the rotor shaft 2 for detecting amagnetic pole position from rotation of the rotor shaft 2 for motorcontrol using an inverter.

The gear section 9 comprises a counter gear mechanism and a differentialmechanism so as to reduce the speed of rotation of the rotor shaft 2 ofthe motor 1 and increase the torque and transmit the rotation to thewheels as rotation in the same direction. The counter gear mechanismcomprises a counter shaft 93 supported at both ends on the gear case 90by bearings, a large-diameter gear 92 fixed to one end of the countershaft 93 and meshed with an output gear 91 fixed to one of the rotorshaft 2, and a small-diameter gear 94 formed together with a second endportion of the counter shaft 93. The differential mechanism comprisesdifferential gears formed of well-known bevel gears, a differential case96 accommodating the differential gears, and a ring gear 95 fixed to thecase 96 and meshed with the gear 94. Both ends of the differential case96 are supported on the gear case 90 by bearings. The differential gearsdisposed in the differential case 96 are connected to the right andleft-hand side wheels (not shown) by universal joints.

The motor case 10 and the gear case 90 accommodating the motor 1 and thegear section 9 constructed as described above are connected to eachother and integrated. The positional relationship between the motor 1and the gears of the gear section 9 thus integrated is shown in FIG. 2,where the position of the motor case 10 is slightly shifted upwardrelative to the position of the gear case 90. In FIG. 2, the position ofeach gear is schematically indicated only by a border line thatindicates the external shape of the gear.

As shown in FIG. 1 and FIG. 2, the supplying means 5 comprises an oilsupply pipe 50 inserted into an end of an in-shaft oil passage 22 of therotor shaft 2, from the side of the gear case 90 connected to the motorcase 10, and the oil receiver 51 connected to the opposite end of thegear case 90, according to this embodiment. The oil supply pipe 50 isbent in the shape of a letter "L", and supported on the case at aportion near the bent. The opposite end of the oil supply pipe 50 isconnected to and supported on the case 90 by the oil receiver 51.

As illustrated in detail in FIG. 3, the oil passage inside the motor 1includes the in-shaft oil passage 22 and radial oil passages 23 formedin the rotor shaft 2 and connected to the in-shaft oil passage 22, andaxial oil passages 32 formed in the core 30 and extending therethroughin the direction of axis, and connection oil passages 24 formed in plate21 that connect the radial oil passages 23 of the rotor shaft 2 and theaxial oil passages 32 of the core 30, and oil holes 25 that areconnected to the axial oil passages 32 of the core 30 and that open toportions of the core 30 located radially inward of the coil ends 41 ofthe stator 4, and the supplying means 5 for supplying oil into thein-shaft oil passage 22 of the rotor shaft 2 (see FIG. 1 and FIG. 2).

As illustrated in detail in FIG. 4, the oil receiver 51 has an upwardopening box shape according to this embodiment, where diagonal cornerportions are cut away so as to avoid interference with outer peripheralportions of the ring gear 95 and the large-diameter gear 92 of thecounter gear and receive oil dragged up by rotation of the gears withouta failure. The oil receiver 51 is positioned close to the outerperipheral portions of the ring gear 95 and the large-diameter gear 92so as to face astride the outer peripheral portions of the gears 95, 92in a stagger manner, and the oil receiver 51 is fixed to the case 20 ata predetermined height such that the oil receiver 51 is positioned atsubstantially the same level as the center axis of the in-shaft oilpassage 22 of the rotor shaft 2 and can receive oil and guide it intothe in-shaft oil passage 22 through the oil supply pipe 50 without usingany special feeding means.

Referring back to FIG. 2, the motor case 10 and the gear case 90 areconnected to each other by the window 52 formed in an end wall of thegear case 10. A lower edge portion of the window 52 functions as a damto maintain the level of oil in the motor case 10, which is recovered ina lower portion of the motor case 10, to a level of a lowermost positionof the outer peripheral face of the rotor 3 indicated by a broken linein FIG. 2. Thus the lower edge portion of the window 52 enables thelower portion of the motor case 10 to function as an oil reservoir. Inaddition, the two cases 10, 90 are also connected to each other by thesmall-diameter orifice 53 formed below the window 52. The orifice 53gradually lets the recovered oil flow into the gear case 90 when the oilrecovery to the lower portion of the motor case 10 is stopped, in orderto balance the oil levels in the cases.

In the drive apparatus constructed as described above, the oil acting asa lubricant and a coolant is mainly held in the gear case 90 up to alevel Lm indicated by an intermediate broken line in FIG. 2. In thisstate, a sufficient oil level is maintained for start operation forwhich the gear section 9 requires more lubricant than for normaltraveling operation. When the motor 1 is started in this state, the ringgear 95 is driven by the motor 1 to rotate counterclockwise, and thelarge-diameter gear 92 of the counter shaft rotates clockwise. The oildragged up by the rotation of the gears is collected into the oilreservoir 51. The collected oil is supplied from the gear case 90 intothe in-shaft oil passage 22 of the rotor shaft 2 guided by the oilsupply pipe 50.

In FIG. 3, flows of oil are indicated by arrows. Oil supplied into thein-shaft oil passage of the rotor shaft 2 as described above flows alongthe peripheral face of the in-shaft oil passage 22 by centrifugal forcecaused by rotation of the rotor shaft 2, enters the radial oil passages23, and flows through the connection oil passages 24 of the plates 21and the axial oil passages 32 of the core 30. The oil is sprayed fromthe holes 25 of the plates 21 to each coil end 41 by centrifugal forceof the rotor 3. Thus, the oil reliably cools the core 30 while flowingone-way through the axial oil passages 32, and then reliably cools thecoil ends 41 at the opposite ends of the stator 4 when discharged fromthe oil holes 25 and supplied to the coil ends 41.

After cooling the motor, oil flows down along the motor case 10 or dripsfrom various portions to gather in a lower portion of the motor case 10.An amount of oil that exceeds the lower edge level of the window 52returns to the gear case 90. Oil that gathers in a portion of the motorcase 10 on a side of the core 40 remote from the gear case joint isguided to the side of the window 52 by some of key grooves formed on themotor case 10 for fixing the core 40 to the motor case 10 in a rotationpreventative manner, that is, some key grooves that are not used for thefixing, according to this embodiment. During operation of the motor, theflowing of oil through the aforementioned oil passages and the likereduces the oil level in the gear case 90 to a level L1 indicated by thelowermost broken line in FIG. 2, and maintains the oil level in themotor case 10 at a level Lh indicated by the uppermost broken line,which enables the maximum cooling of the stator 4 without causing thestirring by rotation of the rotor 3. When the operation of the motor 1is stopped, the flow of oil through the orifice 53 gradually balancesthe two oil levels, so that the oil levels will finally reach the levelLm indicated by the intermediate broken line in FIG. 2.

As described in detail above, the drive apparatus for an electricvehicle utilizes a lower portion of the motor case 10 as an oilreservoir during the running of the vehicle. Furthermore, the driveapparatus is provided with the orifice 53 formed in a lowermost portionof the motor case 10 for returning oil toward the gear section 9 duringstoppage of the vehicle to prepare for a start of the vehicle. Duringthe running of the vehicle, the apparatus lowers the oil level for thegear section 9 to reduce the gear stirring loss, and raises the oillevel in the motor case 10 so that the stator 4 and the coil ends 41 canbe dipped into the oil thus improving the cooling efficiency for themotor 1. During stoppage of the vehicle, the orifice 53 allows oil tomove from the motor 1 toward the gear section 9 to raise the oil levelfor the gear section 9, thus ensuring lubrication for a start. Inaddition, this construction secures a sufficient amount of oil andincrease the heat capacity without increasing the case capacity forinstallation of a reservoir.

Next, FIGS. 5-9 illustrate a second embodiment of the present invention.For a further size reduction of the apparatus from the first embodiment,the apparatus according to this embodiment has a construction where thedistance between the rotor shaft 2 and the differential gears is made asshort as possible. For this construction design, this embodiment employsa consolidated unit of the motor case and the gear case, which areseparate units according to the first embodiment. Thus the secondembodiment also achieves a weight reduction. Although this embodiment issimilar in overall construction to the above embodiment, the change ofthe case formation makes several differences in minute construction.Portions of the second embodiment substantially corresponding to thoseof the first embodiment are denoted by corresponding referencecharacters and will not be described again. The description below willmainly focus on differences.

A motor 1 and a gear section 9 are disposed in a consolidated case body10A, as shown in an actual side view of FIG. 6, in such an arrangementthat a rotor shaft 2 of the motor 1 is positioned substantially abovethe axis of differential gears disposed in a differential case 96 of thegear section 9. As shown in FIG. 5, a motor chamber m of the case 10A isclosed by a front case 10C, and a gear chamber g is closed by a rearcase 10B. The rotor shaft 2 of the motor 1 is freely rotatably supportedat both ends on the case body 10A and the front case 10C by bearings 11.A counter shaft 93 of a counter gear mechanism and the differential case96 are freely rotatably supported at their opposite ends on the casebody 10A and the rear case 10B by bearings. One of yoke shafts 97 (shownby imaginary lines in FIG. 5) engaged with the differential gears in thedifferential gear by spline engagement is supported on the case 10A. Oneend of the yoke shaft 97 is supported by a shaft portion of thedifferential case 96 supported by a bearing 14, and the other end issupported directly by a bearing 13. A large-diameter gear 92 and asmall-diameter gear 94 of the counter gear mechanism has a positionalrelationship which is reversed from the positional relation ship of thecorresponding components according to the first embodiment when viewedin the direction of axis, thereby shifting the position of thedifferential mechanism closer to the motor 1. A size reduction in thedirection of axis is thus accomplished.

As shown in FIGS. 6-8, supplying means according to this embodiment isformed using case walls extending in the case body 10A and the rear case10B. The supplying means comprises an oil receiver 51 which is formedabove the peripheral face of the gear 95 and between an end face 12a ofa partition wall 12 of the case body 10A and a face of the rear case 10Bthat meets the case body 10A and which has a width substantiallyequivalent to the distance between the end face 12a and the meeting faceof the rear case 10B, an oil supply pipe 50 inserted from the side ofthe rear case 10B into an end of an in-shaft oil passage 22 of the rotorshaft 2, and in-case oil passages 50a-50c connecting the two components.The in-case oil passage 50a forms a discharge passage of a gear pumpthat uses the ring gear 95 as a gear-pump gear, and has the same widthas the oil receiver 51. The in-case oil passage 50a has an oil passagearea that decreases toward upward from the oil receiver 51. The oilreceiver 51 is a small-capacity wedge-shape reservoir defined by abottom wall surface formed by a flat face positioned closed to and abovethe peripheral face of the ring gear 95, a side wall surface formed by aside face of the in-case oil passage 50a, the second wall formed by anarc-shaped face extending over the outer periphery of the bearing 11supporting the shaft of the output gear 91 fitted on the outerperipheral face of the rotor shaft 2. The bottom wall of the oilreceiver 51 has a small-diameter oil hole 51a that is connected by aline (not shown) to a lubricating oil passage for a bearing 16supporting the differential case 96. The in-case oil passage 50b is arectangular sectional-shape oil passage extending from an upper level ofthe oil receiver 51 through the inside of the rear case 10B in thedirection of axis. The in-case oil passage 50b reaches an axial end ofthe rotor shaft, via the radial oil passages 50c having a circularcross-section. The in-case oil passage 50b is connected to the in-shaftoil passage 22 by the oil supply pipe 50 that is fitted thereto andfixed by a press plate 50' in a fall-off preventing manner.

This embodiment comprises oil feeding means in order to prevent therotor shaft 2 from floating and moving in the direction of axis. The oilfeeding means uses the spiral rotation of a coil spring 15 compressedbetween an axial end of the rotor shaft 2 and a spring sheet 15a held inthe internal peripheral face of a shaft end portion of the output gear91 in a snap-ring holding fashion In addition, since a lower portion ofthe gear chamber g is considerably expanded in the direction of axisrelative to the width of the ring gear 95 in order to secure an oil sumpcapacity, an improvement of the oil dragging-up effect of the ring gear95 is intended by providing a pair of side plates 54, 55 that extendalong outer peripheral portions of the opposite side faces of the ringgear 95. The side plates 54, 55 are formed of annular press platesprovided separately from the case body 10A and the rear case 10b. Asindicated by their two-dimensional shapes shown in FIGS. 6, 8, acircumferential upper portion of each of the side plates 54, 55 thatdoes not contribute much to the dragging-up effect is cut away. The sideplates are fastened to the case body 10a and the rear case 10Brespectively by bolts.

The oil passages in the motor 1 are constructed substantially the sameas in the first embodiment, but differs in minute constructions. Asshown in FIG. 5, only one side of the core 30 is provided with radialoil passages 23 connecting to the in-shaft oil passage 22 according tothis embodiment. The radial oil passages 23 are connected to axial oilpassages 32 formed in the core 30 through connection oil passages formedin plates 21, reaching oil holes 25 that open in a portion of the core30 located radially inward of the coil ends 41 of the stator 4. Theshape of the motor chamber m is different from the shape of the motorchamber according to the above embodiment. According to this embodiment,an oil sump 56 is provided in the motor chamber m by utilizing aconnection space created by formation of the motor chamber m and thegear chamber g in the case body 10A, that is, expanding a lower endportion of the motor chamber m, mainly, a lower portion of the frontcase 10C.

In this construction, the motor chamber m and the gear chamber g areconnected to each other by a window 52 formed in the partition 12 on theside of the end face 12a of the case body 10A. A lower edge portion ofthe window 52 acts as a dam for maintaining the level of oil gatheringin a lower portion of the motor chamber m at a level corresponding tothe outer peripheral lowermost portion of the rotor 3 indicated by abroken line in the drawing, thus enabling the lower portion of the motorchamber m to serve as an oil reservoir. The lower edge portion of thewindow 52 is inclined according to this embodiment. The inclination isprovided considering the hill-climb running of a vehicle in which theapparatus is installed. Thereby if the case body 10A is inclined with afront portion lifted (the forward direction with respect to theapparatus installed in a vehicle is indicated by reference character F),the embodiment will not cause the oil level in the motor chamber m todecrease but maintain the oil level in the motor chamber m. The motorchamber m of the gear chamber g are connected with each other also bythe small-diameter orifice 53 formed in the partition 12 on the side ofthe peripheral face 12b of the case body 10A at a level (see FIG. 9)lower than the level of the window 52 formed in the partition 12 on theside of the end face 12a, distinguished from the aforementionedembodiment. The orifice 53 acts as in the aforementioned embodiment,that is, allows oil recovered in the lower portion of the motor chamberm to gradually flow into the gear chamber g when the oil recovery isstopped, thus balancing the oil levels in the two chambers.

This embodiment comprises a first return oil passage corresponding tothe return passage formed by a key groove extending across the oppositeends of the stator 4 according to the first embodiment and, in addition,a second return oil passage provided as a separate system in parallelwith the first return oil passage. The first return oil passage isformed as a return oil passage 50d extending along a lowermost portionof the peripheral face of the stator and extending through an outwardlyprotruding portion of the case body along the peripheral face of thestator in the direction of axis, as shown in FIGS. 5 and 9. The secondreturn oil passage is formed as an oil passage extending through ayoke-shaft-97 accommodating portion of a universal joint provided in thegear chamber g. In the second return oil passage, cut-away portions 50e,50f extending in the direction of axis over the outer peripheries of therespective outer laces of the bearing 13, 14 supporting the oppositeends of the yoke shaft 97 are formed downstream of the orifice 53. Theinlet to the oil passage 50d in the oil sump 56 is provided with an oiltemperature sensor 7 for motor control in accordance with oiltemperature.

In the drive apparatus thus constructed, the oil serving as a lubricantand a coolant is held mainly in the gear chamber g up to the level Lmindicated by the intermediate broken line in FIG. 6, as in theabove-described embodiment. Thus this construction secures a sufficientoil level for a start for which the gear section 9 requires morelubrication than for the normal running. When the motor 1 starts tooperate in this state, the ring gear 95 driven by the motor 1 rotatescounterclockwise in FIG. 6, dragging up oil, so that oil is pushed upthrough the oil passage 50a extending along the inner peripheral face ofthe case body 10A and supplied into the oil receiver 51. Unlike theabove-described embodiment receiving splashes of dragged-up oil, thisembodiment forces oil into the oil receiver 51 by using centrifugalforce, so that the flow of oil takes in oil deposited on the internalperipheral face of the case body 10A, thus considerably improving thesupply efficiency. The oil thus collected in the oil receiver 51 isguided to the oil supply pipe 50 via the oil passages 50b, 50c of therear case 10B, and then supplied into the in-shaft oil passage 22 of therotor shaft 2. The further flow of oil on the motor side and its coolingoperation are the same as described in conjunction with the firstembodiment.

After cooling the motor 1, oil flows down along the case body 10A ordrips from various portions, as in the above-described embodiment, togather in a lower portion of the case body 10A, mainly forming a streamthrough the first return oil passage. An amount of oil that exceeds thelower edge level of the window 52 returns to the gear chamber g.According to this embodiment, oil that gathers in a portion of the casebody 10A on a side of the core 40 remote from the gear chamber is guidedto the side of the window 52 through the oil passage 50d. Duringoperation of the motor, the flowing of oil through the aforementionedoil passages and the like reduces the oil level in the gear chamber g tothe level L1 indicated by the lowermost broken line in FIG. 6, andmaintains the oil level in the case body 10A at the level Lh indicatedby the uppermost broken line, which enables the maximum cooling of thestator 4 without causing the stirring by rotation of the rotor 3.According to this embodiment, an axial end of the counter shaft 93positioned at substantially the same level as the window 52 is providedwith an opening extending through the end face 12a of the partition 12.Oil flowing through this opening back into the gear chamber g lubricatesthe bearings of the counter shaft 93.

According to this embodiment, when the operation of the motor 1 isstopped, oil is returned from the oil receiver 51 to the gear chamber gvia the oil hole 51a of the bottom wall of the oil receiver 51 and thebearing 16, and also oil flows from the oil sump 56 of the motor chamberm through the orifice 53 and returns to the gear chamber g forming astream through the second return oil passage. The oil flowing though theorifice 53 flows by an end portion of the gear chamber g, and flowsthrough the oil passage 50e, the accommodation portion for the yokeshaft 97, and the oil passage 50f, and then returns to the gear chamberg, thus gradually balancing the two oil levels. The oil levels finallybecome the level Lm indicated by the intermediate broken line in thedrawing.

As described above, the drive apparatus according to the secondembodiment achieves substantially the same advantages as achieved by thefirst embodiment and, in addition, advantageously improves the oilgathering efficiency of the oil receiver 51. Furthermore, since thelower edge of the window 52 is inclined with a front portion lowered,the level of the lower edge of the window 52 remains substantiallyunchanged on an uphill road, thus excluding the influences of theforward or rearward inclination of the vehicle on the oil level.Furthermore, since the oil temperature sensor 7 is disposed in the oilsump 56 of the motor chamber m for temperature detection, the embodimentadvantageously controls the motor on the basis of precise determinationof the motor load at various time points made from the actual oiltemperature detected after the cooling of the motor.

Finally, FIG. 10 illustrates a modification of the second embodimentwhere the entire supplying means 5 is integrated with the case. In thismodification, a portion corresponding to the oil passage pipe 50constituting the oil passage of the supplying means 5 according to theabove-described embodiment is integrated with the rear case 10B andformed as a tubular oil passage 50g extending from an end of the rearcase 10B and fitted to a shaft hole of the output gear 91. In addition,the snap ring for the spring 15 is shifted to a position near the endface of the tubular oil passage 50g located inwardly of the end of theshaft hole of the output gear 91 and fitted to the shaft hole in thatposition, and the snap ring is used as a spring sheet 15a. Thisconstruction is useful for reducing the gap between the outer peripheralface of the tubular oil passage 50g and the shaft hole of the outputgear 91 in order to reduce oil leak from the supply oil passage. Inaddition, since this construction allows omission of the press plate 50'and the oil passage pipe 50 employed in the above embodiments, thisconstruction is also advantageous in reduction of the number ofcomponent parts and, therefore, reduction of assembly man hours.

While the present invention has been described with reference to theembodiments thereof, the present invention is not limited to theseembodiments. On the contrary, specific constructions of the inventionmay be modified in reduction to practice in various manners included inthe scope of the description in the claims. In particular, the supplyingmeans may be formed by an oil pump that is driven by rotation of thegear section or revolution of the motor.

INDUSTRIAL APPLICABILITY

As described above, the drive apparatus for an electric vehicle of thepresent invention is useful as a drive apparatus for various motorvehicles, and it is particularly suitable for use as a drive apparatusinstalled in an electric vehicle in an on-board fashion.

We claim:
 1. A drive apparatus for an electric vehicle characterized bycomprising a motor (1) including a stator (4) and a rotor (3) having arotor shaft (2) that is rotatable inside the stator, a gear section (9)for transmitting rotation of the rotor shaft to a wheel, and a case (10,90) for accommodating the motor and the gear section, wherein the casehas a partition (12) that separates a motor chamber (m) foraccommodating said motor and a gear chamber (g) for accommodating saidgear section, and the partition has an orifice (53) that connects alower portion of said motor chamber and said gear chamber, and supplyingmeans (5) is provided for supplying oil from said gear chamber into saidmotor chamber in accordance with rotation of said gear section.
 2. Adrive apparatus for an electric vehicle according to claim 1,characterized in that said supplying means comprises an oil receiver(51) for receiving oil in the gear chamber drawn up by rotation of thegear section and guiding the oil into the motor chamber.
 3. A driveapparatus for an electric vehicle according to claim 1, characterized inthat a window (52) connecting said motor chamber and said gear chamberis formed in a position which is above said orifice of the partition andwhich is at substantially the same level as a lowermost position of aperipheral face of said rotor.
 4. A drive apparatus for an electricvehicle according to claim 2, characterized in that a window connectingsaid motor chamber and said gear chamber is formed in a position whichis above said orifice of the partition and which is at substantially thesame level as a lowermost position of a peripheral face of said rotor.